What remains constant in uniform circular motion?
A. Velocity
B. Speed
C. Displacement
D. Direction

Hint: The direction of motion keeps on changing with the revolution, in case of uniform circular motion. In this motion, with the number of revolution displacement from the initial point to the final point changes. As both these factors vary and it is responsible for the change in velocity.

Complete step by step answer:
Physics deals with various types of motions. In daily life, we come across various practical situations involving motion. Circular motion is the special case of linear or translatory motion, in which a particle revolves along the circumference of a circle.
Now we are going to introduce the uniform circular motion.
Uniform circular motion is defined as the motion of a particle along the circumference of a circle with constant speed.
In a uniform circular motion, the direction of velocity is along a tangent drawn to the position of the particle on the circumference of a circle. Hence the direction of velocity goes on changing continuously, however, the magnitude of velocity is constant and we know that magnitude of velocity is nothing but speed.
Thus uniform circular motion can also be defined as the periodic motion of a particle moving along the circumference of a circle with the constant angular speed.
Hence speed remains constant in a uniform circular motion.

So, the correct answer is “Option B”.

Note: In a uniform circular motion, since the magnitude of velocity is constant therefore magnitude of angular velocity is constant. Uniform circular motion can also be denoted as U.C.M. in case of uniform circular motion, speed, radial acceleration, angular momentum, the magnitude of linear momentum remains constant.